As a rule, such microphone elements are subjected to a final acoustics measurement at the end of production, during which compliance with specifications is checked, e.g., the sensitivity, noise, frequency response characteristic and current consumption. A test for the correct functioning of the individual components parts, especially the MEMS and ASIC elements at the wafer level, which is relatively cost-effective, is insufficient in this case since the microphone packaging, i.e., the physical layout and connection technology and the component housing, has an important influence on the microphone performance. The testing costs represent a significant portion of the total cost of the component part.
German Published Patent Application No. 101 54 867 describes one possibility for testing the sensor properties of a micromechanical pressure sensor element. This pressure sensor element includes a sensor diaphragm, which spans a sealed cavity in the semiconductor substrate of the structural element. An electrode, which forms a capacitor together with an electrode on the diaphragm, is situated on the cavity bottom. This capacitor is used not only for the capacitive signal acquisition, but also the selective excitation of the diaphragm. To do so, a defined, i.e., temporally varying, voltage is applied to the capacitor in order to induce vibrations in the sensor diaphragm. The resulting diaphragm deflections are then recorded in terms of quantity and quality with the aid of the capacitor. When the measuring signals obtained in this manner are analyzed, it is possible to draw conclusions regarding the height and extension of the cavity, as well as the mobility and thickness of the diaphragm, its maximum deflectability and its elastic modulus.